U.S. Pat. No. 5,127,765, System for In-Situ Treatment of Underwater Contaminated Material, discloses a method and apparatus for treating contaminated underwater sediment by lowering a hollow square casing to an underground bed, lowering a power-driven Kelly bar with injecting and mixing blade fed with treatment material, such as solidifying cement and flyash, providing a top cover for confining the sediment to be treated within the casing, injecting and mixing the treatment material through the Kelly bar and sequentially moving the square casing with Kelly bar to adjacent treatment locations. Treatment material is discharged from the ends of the blade and mixed primarily within the cylindrical column described by the path of the blade.